The present invention relates generally colonography (also known as computed tomographic colonography or CTC), a minimally invasive imaging technique for colorectal cancer screening. In particular, the invention is a method for generating colonography images that does not require cathartic preparation of the colon prior to the imaging.
Colonography, the use of electronic imaging technologies such as computed tomography (CT) to generate images of a patient""s colon for purposes of colorectal cancer screening, is generally known. Descriptions of this diagnostic methodology can, for example, be found in the Johnson et al. U.S. Pat. No. 5,891,030, the Johnson et al. PCT publication WO 98/32371, the Vining U.S. Pat. No. 5,782,762 and the Vining et al. U.S. Pat. No. 5,920,319, all of which are hereby incorporated by reference. Briefly, this methodology involves obtaining a series of CT images of adjacent portions or slices of the colon. A radiologist then studies each of the images to identify any pre-cancerous polyps. Also known as virtual colonoscopy, this technique effectively creates a computer simulated intraluminal flight through the colon. This dynamic diagnostic methodology has been demonstrated to be a highly efficacious approach for detecting colorectal polyps.
Although these known colonography approaches are generally much less invasive and more comfortable for the patient that other colorectal cancer screening techniques such a colonoscopy, they still require that the patient""s colon be prepared (i.e., cleansed of stool) through the use of laxatives or other cathartics. Removal of the stool is required because the stool exhibits the same density to the imaging processes as the polyps and soft colon tissue. In other words, the stool looks very similar to polyps and the tissues of the colon in the colonography images. The presence of stool can therefore mask polyps and other features in the images that may be relevant to the diagnostic process. Unfortunately, these colon preparation processes can be time consuming and uncomfortable for the patient. Patient compliance with the preparation processes is sometimes therefore poor, resulting in reduced efficacy of the diagnostic procedure. Perhaps even worse, some patients may forego the diagnostic procedure altogether to avoid the inconvenience of the preparation process.
It is evident that there is a continuing need for improved colonography methodologies. In particular, there is a need for colonography methodologies that are less sensitive to the need for thorough colon preparation prior to imaging. A methodology that does not require substantial preparation would be particularly desirable. To be viable, any such method must be highly efficacious and efficient to perform. A colonography approach which meets these objectives could enhance patient acceptance of the diagnostic procedure and reduce the morbidity of colorectal cancer.
The present invention is a highly efficacious and convenient method for generating colonography images for colorectal cancer screening. One embodiment of the invention includes administering to the patient an amount of stool marker which will enable stool present in the patient""s colon to be distinguished from soft tissue. The stool marker can be administered in liquid or pill form. Following administration of the stool marker, the patient""s colon is imaged to generate the colonography images. The colonography images are then processed to mark or remove the marked stool and simulate the preparation of the colon. The images can then be displayed to a radiologist during a diagnosis session.